Impulse circuit



Jan. s, 1932. C, L GOODRUM 1,840,090

IMPULSE CIRCUIT Filed July 31, 1930 winding of' the magnet.

Patented Jan. 5r, 1932 CHARLES L. YGOODRUJYYI, 0F NEW YORK, N. Y.,TORIES, INCORPORATED, OF NEW YORK,

ASSIGNOR TO BELL TELEPHONE LABORA- NfY., .A CORPORATION OF NEW YORKIMIULSE CIRCUIT Application led July 31,

This invention relates to impulse circuits and particularly to thoseemployedin the operation of switches for telephone systems.

The objects are to improve the operating conditions of holding relays,to render these relays less liable to release while impulses are beingreceived, to render the adjustments of these relays easier to meet, andto otherwise improve the effectiveness and reliability of impulsecircuits.

Heretofore it has been the usual practice' to arrange the impulsecircuits of step-bystep switches suoli that the holding and re-` leaserelay receives its operating energy over a circuit closed through thefront contact of the impulse relay. Since the impulse relay releases andoperates successively in response to a series'of impulses, the circuitof the holding relay is opened on each successive impulse from the timethe impulse relay opens its front contact until this contact is againclosed. To prevent it from retracting its armature during theseopenings, the holding relay is constructed so asto release slowly.

f" However, it has been found that unless the relay is properly adjustedit will lose enough energy on a long series of impulses to release, thuscausing improperoperation of the apparatus.

According to the present invention, these defects are overcome by meansof an arrangement in which the holding relay receives energy from twoseparate circuits, one of which is closed over a front. contact and theother of which is closed overa back contact of the impulse relay. Withthe impulse Vrelay energized, theholding relay is maintained operatedover the usual circuit extending through the front contact of theimpulserelay. Each time the impulse relay releases its armature todeliver .impulses to the vertical stepping magnet, a circuit is closedover the back con# tact of said relay through a second winding on theholding relay and'thence through the The holding relay receives energyin this circuit until the vertical magnet has partially operated,at'which time the second winding ofthe holding relay is shunted. v

The advantage of this circuit arrangement lin the usual manner to setits 1930. Serial No. 471,909.

is that the holding relay receives energy over both front and backcontacts of the impulse krelay and,\therelore, will not accidentallyrelease while impulses are being received, whether the series consistsof a. few impulses or the maximum numberr of impulses.

In the drawings Fi g. 1 represents a portion of an automatic telephonesystem in which the circuits for one of the selector switches are shownin detail, other equipment being illustrated diagrammatically. Figs. 2and 3 show alternative circuit arrangements.

`Considering Fig. 1 first, a subscribers line 1 appears at the centraloflice in a suitable switching device such as a line finder F. Vhen theline calls, the finder F is operated brushes 3, 4 and 5 on the terminalsof the line 1, thereby extending said line to a selector switch such asthe selector S having'the brushes 10, l1 and 12. As soon as thesubscribers line is extended to the selector S, a circuit is closed forthe impulse relay 13 and may be traced from battery, through theleft-hand winding of said relay, inner upper back contact of relay 9,conductor 7 brush`4, thence over the loop of the calling line andreturning through the brush 3, conductor 6, uppermost back contact ofrelay 9, right winding of relay 13, contacts 2l, through the secondarywinding of the tone coil 22 to ground. The relay 13 operates and closesan energizing circuit for the holding relay 14. This circuit may betraced from ground, through the lowermost contact of relay 9, frontcontact of relay 13, upper Winding of relay 14 to battery. The relay 14,which controls the release of the switch S-,is designedwith aslow-release characteristic in lorder that it will maintain itsarmatures in their attracted position during the intervals that itis de`prived of'energizing current while impulses are being received.

lThe coil 22 causes a tone to be transmitted to the subscriberssubstation Vto notify him that impulses may be transmitted. In responseto this tone, theV subscriber manipulates his dial Q. to send a seriesof impulses representing a digitalplace in the wanted designation. Onthe first opening ofthe subscribers line by the impulse transmitter 2,the impulse relay 13 releases its armature, lirst opening its frontcontact and immediately thereafter closing its back Contact. The openingolf the trent contact of relay 13 results in 'the opening o' theenergizing circuit oi? the holding relay 1l, and this relayeonnneneei-I; to lose energy. However, due to its slow-releasingcharacteristic, it will retain its armatures. Relay 13 at lits baci;contact closes a circuit for delivering the linst impulse to thevertical stepping magnet 16. This circuit may be traced from ground,through the lowermost contact ot relay 9, back contact et relay 13,inner front contact and winding ot holding relay 114-, winding olf relay15, winding of the magnet 16 to battery. Current flowing in this circuitenergizes the relay 15 and the vertical magnet 16 which attracts itsarmature to move the brush sha'tt one vertical step. T he relay 15 isslow to release and maintains its armature attra0ted during a series otimpulses. Since the lower winding ot the holding relay 111 is alsoincluded in series with the magnet 16, additional energy is supplied tothe relay 111 to replenish the energy lost during the momentary openingof its original energizing circuit. The magnet 16 also closes thecontact shown and in so doing shunts the lower winding ot' the holdingrelay lll. The shunt circuitmay be traced from ground, through the lowerarmature of relay 9, back contact of relay 1?), inner contact ot relay111, contact of' magnet 16, thence through the windings oi': relay 15and magnet 16 to battery. rfhe contact of the magnet 16 is so adjustedthat it closes slightly betere the vertical pawl seats .itselt in theratchet on the brush shaft. The purpose ot' this will be explained morein detail hereinafter. 'if he closure ot the shunt around the lowerwinding of relay 1K1 tends to maintain the fini; in that winding so thatthe energy is not dissipated imme-4 diately. The vertical magnet 16,continuing its stroke in the circuit which now excludes the lowerwinding ot the relay 14;, advances the brushes to a full step.

As soon as the switch takes its first vertical step the contacts 2() areclosed, and relay 17 energized in a circuit from battery, through itswinding, upper contacts 20, closed contacts of relay 15, conductor 25 toground at the lower contact of relay 111. Relay 17 operates and locks ina circuit from battery, through its winding, upper contacts 20, con tactof the rotary magnet 18, upper contact ot relay 17, conductor 26 toground at the lowermost contact of relay 9.

At the end of the first impulse, the line is again closed., and relay 13operates to shift its armature from the back contact to the frontcontact. Relay 14 is now again supplied with energy over its upperwinding,

" and the energizing circuit ot magnet 16 and relay 5 is temporarilyopened. Magnet 16 immediately releases its stepping armature and alsoopens its contact, removing the shunt 'from the lower winding o't therelay 1d. For each succeeding impulse in the series, the relay 13releases and delivers an in'ipulse to the magnet 16 over a circuit whichextends lirst through the lower winding of relay 1st and then in shuntot' said winding, through the relay 15 and the winding ot the magnet 16.ln this manner the switch stepped vertically to the proper level, andduring the stepping operation relay lll1 is successively supplied withenergy through its upper and lower windings.

At the end of the impulse series, the line is re-closed for a longinterval., and relay attracts and holds its armature against the frontcontact. After an interval, relay 1o releases its armature and in sodoing prepares an energizing circuit tor the rotary magnet 18 to advancethe brushes 10, 11 and 12 over the contacts ot the selected group. Thecircuit tor the magnet 1S may be traced from battery through the windingof the magnet, lower contact of relay 17, normal contacts of relay 15 tothe grounded conductor 2 The magnet 18 energizes and steps the brushesonto the lirst set of contact-l, .n the group. Magnet 18 also attractsits armature and opens the holding circuit oil relay 1T. Relay 17immediately releases and opens the energizing circuit o1 the magnet 18,whereupon the magnet releases preparatory to taking the next rotarystep. li the circuit appearing in the iirst set ot contacts is busy, thetest brush 12 encounters a ground potential on the test terminal, andthe relay 17 is reenergized in the following circuit: Battery, throughthe winding of? said relay, pper contacts Q9, normal con tacts ot magnet1S, conductor 2T, inner lower back contact oit relay 9, conductor 2S tothe grounded test brush 12. A parallel circuit may be traced frombattery, through the winding ot relay 17, rpper Contact 20, contact oilthe magnet 19, conductor 27, winding et switching relay 9, uppercontacts 21 to the ground ed ctmductor 25. Since there is a directground potential on the brush 19, relay 9 is shunted and does notoperate. Relay 1T in operating rocloses the circuit of the magnet 18,which advances the brushes another step and opens the circuit ol rela-y17. Relay 1T releases, in turn releasing the magnet 18. This actioncontinues until the test brush 1i! encounters an idle terniinal, whichis represented by the absence olI ground potential. At this time, theshunt is removed from the winding ot' relay 9, and said relayimmediately energizes. Relay 17, however. does not energize .in thiscircuit due to the rcsistance ot relay 9; accordingly the circuit ot thestepping magnet 18 is maintained open,

and the switch ceases to advance, coming to rest on the terminals of theidle circuit.

Relay 9 in operating switches the tip and ,ring conductors of thecircuit through the brushes 10 and 11 and thence to the next sucrelay 9energized. J

, cuit for the release ceeding switch. Relay 9 by attracting itsarmatures opens the circuit of relay 13 which releases its armature.After an interval, ieflay 14'releases since no current flows through 5either its upper or lower windings. Before relay 14 can release toremove ground fromA When it is desired to release the selector S,groundpotential is removed fromthe conductor 28, thereby permitting therelease ot' relay 9. Relay 9 closes an energizing cirmagnet 19 traceablefrom battery, through the winding of said magnet, lower contacts 20,inner back contact of relay 14, back contact of relay '13, lowermostcontact of relay 9 to ground. The r-e- ^lease magnet 19 energizes andreleases the "switch S. When the switch fully restores, the verticaloff-normal contact 20 is opened, and the magnet 19 deenergizes.

The condenser Q9 and lresistance 30 are provided for the purpose ofprotecting the *Contact of relay 13 during the vertical pulsingoperation and the lower contact of relay 17 during the rotarysteppingmovement. The lower plate of the conductor 29 is conn nected inparallel with the impulse circuit extending to the verticaly magnet 16,and the upper plate of said condenser is connected in parallel with theimpulse circuit of the rotary magnet 18. f

Should the subscriber abandon the call betore transmitting impulses tothe switch, relay` 13 releases, closing the circuit hei-einbefore tracedthrough the lower Winding of relay 14, winding of relay 15 and windingof magnet 16 to battery. The magnet short-circuits the lower winding ofrelay 14, and, since the upper winding is deenergized, the relayreleases after an interval causing the restoration of the switch. Shouldthe subscriber abandon the call durinO'V the rotary' movement of theswitch, relay 13 releases and completes a circuit fromground through thelowermost contact of relay 9, back contact of relay 13, thence as tracedthrough the windings of relays 14 and 15 and the magnet 16 to battery.Inasmuch as the brushes of the switch are now in the level of terminals,

the magnet 16 will not be able to advance its stepping dog a full step.Since, however, the magnet closes its contact just before the steppingdog is fully seated in the vertical and the inner lower ratchet, thelower winding of the relay 14 is certain to be short-circuited underthese conditions. Therefore, after an interval the relay 14 deenergizesand closes the release eircuit to restore the switch to normal.

Figs. 2 and 3 illustrate modiiications of the pulsing circuit. lnFig. 2,a rotary off-normal contact 23 is provided and opens as soon as theswitch has taken its iirst rotary step. ln Fig. 3, the rotary oil-normalcontact 24 closes as soon as the switch has taken is first rotary step.By providing these rotary offnormai contacts, it is possible to adjustthe contact on the vertical magnet 16 so that it closes later in thestroke, namely, just about the time the magnet has completed the fullforward movement of the shaft. With the circuit shown in Fig. 2, shouldthe subscriber abandon the call during the rotary movement,

no impulse can be delivered to the vertical magnet 16, and consequentlycurrent is not caused to tlowptl rough the lower relay 14 due to thefact tl e contact 23 is open.Y After an interval therefore, the holdingrelay 14. releases and causes the restoration of the switch. Similarlyin Fig. 3, should the subscriber abandon the call during the'rotarymovement, an impulse is delivered to the vvertical magnet, but, sincethecontacts 24 are closed, the lower winding of relay 14 is shunted andconsequently this relayis not held energized by reason of its lowerwinding. The circuit for the magnet 16 in this case extends through thearmature and contact of relay 14, contacts 24, winding of the magnet 16to battery.

The finder F and the selector switch S disclosed in this application.may be of any suitable construction. Selcctor S is preferably of thetwo-movement step-by-stepA type, having a first stepping movement toselect groups of trunks or lines and a second stepping movement toselect individual trunks or lines. A switch ot' this general characteris disclosed in the patent to Keith et al. No. 815,- 876, granted March13, 1906.

lVhile the invention has been illustrated in connection with a specificcircuit .arrangement, it is to be understood that it is not limited tothese particular circuits. It should also be noted that this inventionis applicable to repeaters for repeating impulses from an incomingcircuit to an outgoing circuit and that it is also applicable toconnector switches in which both the primary and secondary movements aredirectively controlled by impulses. y

What is claimedis:

l; The combination in an impulse circuit of an impulse relay, a steppingmagnetre-` sponsi've toimpulses delivered by said relay,

a holding relay, -a circuit including the front contactof the impulserelayfor supplying energy to 'said holding relay, and a circuit windingot including a back contact of the in'ipulse relay 'for supplying energyto said holding relay.

2. 'Ihe combination in an impulse circuit of an impulse relay, a sourceof current, a.

l holding relay, a circuit closed b 'T said im- 'pulse relay whenenergized for supp lyin current from said source to the holding relay,.and a circuit closed by said impulse relay when released 'lor supplyingcurrent from plying energy to said holding relay.

3. In combination, an impulse relay, a holding relay, a circuitincluding the Yl'ront contact ol" the impulse relay lor supplying energyto said holding relay, and a circuit including a back contact or theimpulse. relay and a contact of the holding relay Alor supplying energyto said holding relay.

si. In combination, an impulse relay, a stepping magnet responsive toimpulses delivered by said relay, a control relay, ya circuit includingthe iront contact or the impulse relay for operating said control relay,and a circuit including the back contact oif the impulse relay forsupplying.energyto said control relay and for delivering an nnpulse tosaid magnet.

In combination, an impulse relay, a stepping magnet responsive toimpulses, a control relay, a circuit including the iront contact of theimpulse relay for operating said Control relay, a circuit including aback contact of the impulse relay 'for delivering operating impulses tosaid magnet, and a winding for the control relay in said last mentionedcircuit.

6. In combination, an impulse relay, an operating magnet responsive toimpulses delivered by said relay, a control relay, a circuit closed bythe front Contact of the impulse relay or operating said control relay,a circuit including a back contact of the impulse relay and a contact onthe control relay for delivering impulses to said magnet, and means insaid last mentioned circuit for supplying energy to said control relay.

7. In combination, an impulse relay, a holding relay having two windingsthereon, a circuit closed at a front Contact o the impulse relay forenergizing one of said windings, and a circuit closed at the backcontact ot said impulse relay and a front cont-act of said holding relayfor energizing the other of said windings.

8. In combination, an impulse relay, a stepping magnet, a holding relayhaving two windings, a circuit closed at the front contact of theimpulse relay for energizing one of said windings, and a circuit closedat the back contact of said impulse relay for energizing said steppingmagnet and the other of said windings. Y

9. The combination in an impulse circuit of an impulse relay, a steppingmagnet responsive to impulses delivered by said relay, a holding relay,a circuit including the front Contact of the impulse relay for supplyingenergy to said holding relay, a circuit including a back Contact of theimpulse relay for supplying energy to said holding relay, and meanscontrolled by said magnet for pre venting the `further supply of energyin said second circuit to the holding relay.

lO. The combination with an impulse relay oi a stepping magnetresponsive to said relay, a holding` relay, a source or' current, acircuit closed by the 'front Contact of the impulse relay for supplyingcurrent to the holding relay from said source, a circuit closed by theback contact of the impulse relay for supplying current to the holdingrelay from said source, and means controlled by said magnet for shuntingthe current in said second circuit awa-y from said holding relay.

11. The combination in an impulse circuit of an impulse relay, astepping magnet responsive to impulses from said relay, a hold ing relayhaving two windings, a circuit closed by the 'liront Contact of theimpulse relay for one of said windings, a circuit closed by the bachcontact or' the impulse relay for the other of said windings, andcontacts closed by the operation or'. said stepping magnet forshort-circuiting said second winding.

12. In combination, an impulse relay, a holding relay havingslow-to-release characteristics, a circuit including the :iront contactoit the impulse relay :tor supplying energy7 lo said holding relay, anda circuit including the back contact of the impulse relay, and a contactof the holding relay for supplying energy to said holding relay.

lil. In combination, an impulse relay, a stepping magnet responsive toimpulses delivered by said relay, a control relay having slmv-towreleasecharacteristics, a circuit including the front contact of the impulse relay for operating said control relay, and a circuit including the backcontact olf the impulse relay for supplying energy to said con* trolrelay and ior delivering an impulse to said magnet.

In witness whereof, I hereunto subscribe my name this 28th day of July,1980.

CHARLES L. GOODRUM.

